1. Field of the Invention
This invention relates to mechanism for latching a damper plate to prevent movements thereof which may produce irregular and undesired circuit operation, and, more particularly, to means for automatically latching the damper when moved to its open position and for automatically releasing the damper latch upon the initiation of forces for moving the damper to its closed position; however, this invention is not necessarily so limited.
2. Prior Art
U.S. Pat. No. 3,580,238, issued to Diehl, is representative of prior art damper devices in which a flue damper is biased to a closed position by yieldable means, such as a spring, and electrically driven to an open position by motive means, such as a solenoid. A difficulty with such devices is that upon a power failure, the damper apparatus fails to a closed position with the result that the damper mechanism may block the release to the atmosphere of combustion products which are desired to escape the flue being regulated. U.S. Pat. No. 4,039,123, issued to Frankel, is representative of various prior art devices which overcome the limitations of the aforementioned Diehl patent by causing a yieldable means or spring to bias the damper to an open position, with the result that upon any power failure the damper mechanism fails open, thus releasing any combustion products not yet exhausted.
In devices of the fail-open type, a yieldable means, such as a spring, holds a damper plate in an open position. Frequently, however, the open position is an unstable position, with the result that the damper plate may bounce or chatter and thereby undesirably affect associated control circuitry.